1. Field of the Invention
The present invention relates to a sanitary napkin having a main body capable of absorbing and retaining liquid and rear flaps projecting laterally in opposite directions from a rear part of the main body and more particularly to a sanitary napkin whose rear flaps when worn easily deform in accordance with the body shape of a wearer, feel good to the touch and are resistant to wrinkling.
2. Description of the Related Art
Sanitary napkins have a main body with a liquid absorbent layer interposed between a liquid-permeable topsheet and a liquid-impermeable backsheet. When the main body is applied to the crotch region of a woman, liquids discharged from the vaginal opening can be absorbed by the liquid absorbent layer through the topsheet.
Such sanitary napkins include elongated ones which are designed such that the vaginal opening may face a front part of the main body and the intergluteal cleft (i.e., the furrow of the buttocks), as well as the anus, may be covered with a rear part of the main body. Typically, the elongated sanitary napkins are provided with rear flaps projecting laterally in opposite directions from the rear part of the main body. When a wearer is sleeping on her back or sitting for a long time, for example, menstrual blood tending to migrate posteriorly from the vaginal opening can be absorbed by the rear part of the main body of the sanitary napkin and furthermore menstrual blood tending to flow out laterally from the rear part of the main body can be received by the rear flaps, which prevents an undergarment from being stained.
When the sanitary napkin is worn, the rear flaps, which are kept in an unfolded state and laid on an inner side of an undergarment, come into close contact with the wearer's body. However, if the wearer's legs move during wearing of the sanitary napkin, the body shape will change in the crotch region and the buttocks and therefore the undergarment will be partially stretched or twisted to exert a deforming force on the rear flaps. This results in twisting or wrinkling the rear flaps during wearing of the sanitary napkin.
Japanese Unexamined Patent Publication No. 2003-339765 discloses a sanitary napkin in which stiffness of the rear flap is increased by forming a great number of embossments in a nonwoven fabric used for the rear flap. More specifically, the rear flap is constructed by laying a nonwoven fabric on a body surface of a resin film (backsheet). The rear flap is held between a pattern roll with a given pattern of projections and a roll with a smooth peripheral surface, so that the laminate is locally pressed against the smooth peripheral surface by the projections to have the embossments with increased density. This leads to increasing the stiffness of the rear flap. Patent Publication No. 2003-339765 discloses that the embossments in the rear flap may extend laterally or obliquely in a striped patter or may extend in a lattice pattern.
However, if the stiffness is increased by forming a great number of embossments in the rear flaps as disclosed in Patent Publication No. 2003-339765, the rear flaps, which are kept in an unfolded state on the undergarment, tend to resist deformation in accordance with the wearer's body shape, which may cause an unpleasant feeling. Particularly when the embossments extend laterally in a striped pattern, the rear flaps tend to resist bending in the lateral direction. In addition, the front parts of the rear flaps are typically positioned to face the inner thighs, whose surface shape tends to change as the legs move. Therefore, if the stiffness is increased in the front parts of the rear flaps as disclosed in Patent Publication No. 2003-339765, the front parts tend to resist deformation in accordance with the body shape, which may give an unpleasant feeling to the thighs and result in an uncomfortable fit.
On the other hand, Japanese Unexamined Patent Publication No. H09-500558 discloses a sanitary napkin in which flaps projecting laterally in opposite directions from a main body have first regions where a sheet is corrugated. In the first region, hills and valleys extend linearly and longitudinally. In FIGS. 6 and 7 of Patent Publication No. H09-500558, moreover, the flap is provided not only with the first region but also with a second region which is less expandable and extends laterally.
However, the flaps disclosed in Patent Publication No. H09-500558 are intended to project outwardly from the side edges of the crotch region of an undergarment when the main body is attached to the inner side of the crotch region of the undergarment. The reason for providing the first region in the flap is such that the flaps may be easily folded back against the outer side of the undergarment when the undergarment is pulled up with the main body mounted on the inner side of the crotch region of the undergarment.
That is, the flaps disclosed in Patent Publication No. H09-500558 are not intended to be kept in an unfolded state on the inner side of the undergarment when worn. In addition, the corrugated first region is not aimed at facilitating deformation of the unfolded flaps in accordance with the body shape.